The scatter graph shows the number
of ice creams sold per day from an ice cream van and the maximum daily
temperature. One of the points is an
outlier. State the coordinates of the
An outlier, sometimes called an
anomaly, is a value that is noticeably smaller or larger than the rest of our
results. We sometimes choose to omit these
when analyzing our data, if they are likely to significantly change, for example,
the value of the mean.
You’ll need to use your judgement
here and look for the coordinate that seems to be out of place. In this case, that coordinate lies
at 20, 10. The coordinate of the outlier is
What type of correlation is shown
for the rest of the points? Notice how this question is asking
you to describe the type of correlation the data is showing you. It is, therefore, not enough to say
as the temperature increased, so did the number of ice creams sold. We have to use the word “positive,”
“negative,” or “no correlation.”
In fact, this is an example of
positive correlation. We know because the line of best
fit would slope upwards. A scatter graph with negative
correlation would have a line of best fit sloping downwards.
Estimate the number of ice creams
sold on a day with a maximum temperature of 15 degrees Celsius. Notice how part c has two potential
marks available for it. It is really useful to get into the
habit of drawing a line of best fit for scatter diagram questions, as this is where
the first mark will be awarded. Then and only then can you read
your values from the graph.
Here we find 15 degrees on the
𝑥-axis and draw a line up until we meet our line of best fit. Then we draw a horizontal line from
this point to the 𝑦-axis. You can see, therefore, that an
estimate for the number of ice creams sold is 21.
Michael states that more ice creams
are sold on warmer days. Does the scatter graph support his
claim? Give a reason to support your
You have a number of options with
regards to how you choose to word this question. However, when we are interpreting
scatter diagrams, it is useful to describe the correlation and what it means in the
context of the question. Here the graph shows a positive
correlation, meaning that the higher temperature will indeed lead to a larger number
of ice creams sold.